The long-term objective of this proposal is to increase our knowledge of hereditary and degenerative diseases of the retina and choroid through the application of non-invasive techniques. Ultrasonic spectral biometry will be used to study selected patient populations with these diseases. Reflectivity profiles of the posterior coats will be constructed with a micromillimeter resolution, using unique methods of signal processing which permit depiction of the impulse response of these tissue layers by analysis of interference fringes. A population of diabetic subjects will be studied prospectively to establish alterations in these profiles during the evolution of diabetic retinopathy.